[1.7.x] Fixed #23605 -- Fixed nested subquery regression

Added relabeled_clone() method to sql.Query to fix the problem. It
manifested itself in rare cases where at least double nested subquery's
filter condition might target non-existing alias.

Thanks to Trac alias ris for reporting the problem.

Backport of 5c481db29572a387651681b43d5d4523f96b3793 from master

2 files changed, 21 insertions, 2 deletions

diff --git a/django/db/models/sql/compiler.py b/django/db/models/sql/compiler.py
index d8697fa06d..90ac90f9ae 100644
--- a/django/db/models/sql/compiler.py
+++ b/django/db/models/sql/compiler.py
@@ -56,7 +56,7 @@ class SQLCompiler(object):
         if name in self.quote_cache:
             return self.quote_cache[name]
         if ((name in self.query.alias_map and name not in self.query.table_map) or
-                name in self.query.extra_select):
+                name in self.query.extra_select or name in self.query.external_aliases):
             self.quote_cache[name] = name
             return name
         r = self.connection.ops.quote_name(name)
diff --git a/django/db/models/sql/query.py b/django/db/models/sql/query.py
index c29b08556f..4c60a3b09e 100644
--- a/django/db/models/sql/query.py
+++ b/django/db/models/sql/query.py
@@ -114,6 +114,10 @@ class Query(object):
         # type they are. The key is the alias of the joined table (possibly
         # the table name) and the value is JoinInfo from constants.py.
         self.alias_map = {}
+        # Sometimes the query contains references to aliases in outer queries (as
+        # a result of split_exclude). Correct alias quoting needs to know these
+        # aliases too.
+        self.external_aliases = set()
         self.table_map = {}     # Maps table names to list of aliases.
         self.join_map = {}
         self.default_cols = True
@@ -241,6 +245,7 @@ class Query(object):
         obj.model = self.model
         obj.alias_refcount = self.alias_refcount.copy()
         obj.alias_map = self.alias_map.copy()
+        obj.external_aliases = self.external_aliases.copy()
         obj.table_map = self.table_map.copy()
         obj.join_map = self.join_map.copy()
         obj.default_cols = self.default_cols
@@ -335,6 +340,11 @@ class Query(object):
             # Return value depends on the type of the field being processed.
             return self.convert_values(value, aggregate.field, connection)
 
+    def relabeled_clone(self, change_map):
+        clone = self.clone()
+        clone.change_aliases(change_map)
+        return clone
+
     def get_aggregation(self, using, force_subq=False):
         """
         Returns the dictionary with the values of the existing aggregations.
@@ -788,7 +798,9 @@ class Query(object):
             ident = (change_map.get(ident[0], ident[0]),) + ident[1:]
             self.join_map[ident] = aliases
         for old_alias, new_alias in six.iteritems(change_map):
-            alias_data = self.alias_map[old_alias]
+            alias_data = self.alias_map.get(old_alias)
+            if alias_data is None:
+                continue
             alias_data = alias_data._replace(rhs_alias=new_alias)
             self.alias_refcount[new_alias] = self.alias_refcount[old_alias]
             del self.alias_refcount[old_alias]
@@ -815,6 +827,9 @@ class Query(object):
                 data = data._replace(lhs_alias=change_map[lhs])
                 self.alias_map[alias] = data
 
+        self.external_aliases = {change_map.get(alias, alias)
+                                 for alias in self.external_aliases}
+
     def bump_prefix(self, outer_query):
         """
         Changes the alias prefix to the next letter in the alphabet in a way
@@ -1048,6 +1063,9 @@ class Query(object):
         elif isinstance(value, ExpressionNode):
             # If value is a query expression, evaluate it
             value = SQLEvaluator(value, self, reuse=can_reuse)
+        # Subqueries need to use a different set of aliases than the
+        # outer query. Call bump_prefix to change aliases of the inner
+        # query (the value).
         if hasattr(value, 'query') and hasattr(value.query, 'bump_prefix'):
             value = value._clone()
             value.query.bump_prefix(self)
@@ -1509,6 +1527,7 @@ class Query(object):
             lookup = lookup_class(Col(query.select[0].col[0], pk, pk),
                                   Col(alias, pk, pk))
             query.where.add(lookup, AND)
+            query.external_aliases.add(alias)
 
         condition, needed_inner = self.build_filter(
             ('%s__in' % trimmed_prefix, query),